This invention relates to medical electrical stimulation electrodes in general, and to defibrillation electrodes in particular.
In the past years, there has been substantial activity toward development of a practical, implantable defibrillator. Most proposals involve the use of large surface area implantable electrodes, either to be mounted within the heart, on the exterior of the heart, or subcutaneously. One common approach of providing a large surface area electrode is to employ an elongated exposed coil of biocompatible metal. In the context of an endocardial lead, this is disclosed in U.S. Pat. No. 4,161,952 issued to Kinney et al. In the context of an epicardial electrode, this is disclosed in the context of U.S. Pat. No. 4,187,634 issued to Holleman et al.
In an endocardial lead, an elongated coil serving as the electrode, can be mounted around the exterior of an insulative lead body. It is believed desirable in this context to stabilize the electrode coil with respect to the lead body, both to provide mechanical integrity and to prevent fibrous ingrowth around the individual coils of the electrode. In the above-cited Kinney et al patent, this is accomplished by molding the exposed electrode coil into the surface of the lead body. The entire exterior surface of the electrode may then be machined to provide a smooth surface of alternating conductive areas from the electrode coil and insulative areas from the lead body.